Keypad locks are becoming widely accepted in the residential market. However, many of the locks currently in the market are too large to fit with storm doors or are too bulky to provide good aesthetic appeal. A further barrier to customer acceptance occurs in designs that require additional holes to be drilled into a door in addition to the standard residential bored door prep. These deficiencies deter customers from upgrading their traditional mechanical locks to digital keypad locks. Therefore a need exists for a keypad lock that overcomes theses known installation problems.
Additional problems associated with electronic locks derive from different and conflicting goals for various parts of the lock. For example, the height of a keypad lock cannot be so high that it can no longer fit the space between the main door and the storm door. A lock suffers cosmetically as this height grows; low profile locks are more readily accepted and desired than relatively high profile locks. This preference for low profile locks is in direct conflict with a goal of allowing a standard key cylinder to provide a mechanical override means for the consumer to gain entry when the electronic functions of the lock are not available or desired. The conflict is also related to the relatively long length of standard key cylinders in relation to a typically desired low profile lock thickness or height. Often the cylinder is more than two times as long as the desired lock thickness.
This conflict is further exacerbated by a need or goal of having no new holes in the door in addition to the standard residential door prep. The space under the relatively shallow thickness of the escutcheon and in the 2-⅛ inch diameter hole are the only spaces that can accommodate the lock components such as the cylinder, latch bolt, transmission parts, clutch parts, keypad, PCB, battery, passage mode switch and others.
A digital keypad lock incorporates several mechanisms and has three main components. The first component is a mechanical transmission that functions to transfer the input torque generated by rotating knobs or levers on either side of the door to the bolt or bolt latch that secures the door. Second, an electro-mechanical clutch mechanism is used to engage and disengage the transmission system so that input torque is allowed to be transmitted to the bolt latch only at the appropriate time. The third component of the digital keypad lock is an electronic programmable controller that receives input signals from the keypad or other known input devices. It performs credential checking and initiates commands to activate the electromechanical clutching in response to an authorized credential being presented.
The electro-mechanical clutch mechanism typically includes a directly actuated locking member or a clutch mechanism that connects and disconnects an exterior thumb turn or an exterior handle. The clutch mechanism also typically includes a movable member that releasably couples with the thumb turn or exterior handle, and an electronic actuator that controllably displaces the movable member in response to control signals from the electronic programmable controller. The clutch mechanism typically operates in response to an authorized input, such as a code entered in a keypad or by a swipe card. The authorized input is typically received by the controller, which then generates and transmits a control signal to the actuator that in turn operates the movable clutch member.
The transmission of input motion from the thumb turn or lever to cause the desired effect upon the door securing bolt is performed through the coordination of all the moving parts in the system. All these parts must be synchronized in motion throughout the entire operation cycle, from the time the input thumb turn or lever is activated until the time all of the components return back to their home position. Non-synchronization in any one of the moving parts may cause the lock to not function as intended.
For keypad locks utilizing levers a pre-defined, at-rest orientation for each thumb turn or lever is typically included, and with a horizontal orientation. When the levers sag or otherwise are out of adjustment, the transmission will cause the clutch elements to become misaligned. In this case when a valid code is presented to the controller and the electro-mechanical clutch is commanded to engage, the latch will fail to respond to the turning of the lever because the clutching elements were not in alignment and ready to receive their respective engaging surfaces. This problem can hinder the locking and unlocking functions, as well as cause security and safety concerns for users.
Such door locks also typically include a mechanical override mechanism that is intended to be used when power is lost to the controller, or when the controller or other electronic component malfunctions. Examples of such conventional electromechanical door locks are described in United States Patent Publication 2007/0157684 entitled “Manual Override Mechanism for Electromechanical Locks”.